Terahertz wave detection device, terahertz wave detection method, and terahertz wave detection system

ABSTRACT

Terahertz wave detection equipment comprises: a terahertz wave transceiver including a transmitter for transmitting a terahertz wave and a receiver for receiving a reflected terahertz wave reflected by a background reflected object which exists behind an object to be analyzed; a display; and an information processing apparatus, wherein the transmitter irradiates a terahertz wave based on a transmission signal including a specific frequency toward a two-dimensional area including the object to be analyzed, and the information processing apparatus is configured to analyze concentration of the object to be analyzed based on the reflected terahertz wave and generate a composite image in which a concentration image of the object to be analyzed is combined with an image of the background reflected object.

TECHNICAL FIELD

The present invention relates to terahertz wave detection equipment, aterahertz wave detection method, and a terahertz wave detection system.

BACKGROUND ART

It has been known that a plurality of types of VCO gas shows acharacteristic frequency absorption spectrum in a region of a terahertzwave (0.1 THz to 10 THz, hereinafter referred to as “THz wave”). It hasbeen also known that the THz wave has a longer wavelength than infraredlight, and thus is less susceptible to influence of aerosol. Non-PatentLiterature 1 discloses investigation for applying a THz wave to analysisof VCO gas by using property of the THz wave.

CITATION LIST Patent Literature

-   Non-Patent Literature: Gapless THz Comb Spectroscopy (The Review of    Laser Engineering, Vol. 42, No. 9, pp. 1 to 6, September, 2014)

SUMMARY OF INVENTION Technical Problem

Non-Patent Literature 1 mentions generation of a terahertz wave withouta gap between spectrums, however, does not teach display of a resultwhich is obtained by the analysis using the THz wave. Since a terahertzwave has a longer wavelength than light, resolution of an image of thereceived terahertz wave cannot be the same level as that of a visiblelight image. Accordingly, improvement is necessary for providing aresult of the analysis using the THz wave as an image.

The present invention has been made in view of the circumstancesdescribed above, and an object of the present invention is to providedisplay technique capable of making it easy to see an analysis resultusing a terahertz wave.

Solution to Problem

In order to solve the problems described above, the present inventionprovides terahertz wave detection equipment comprising: a terahertz wavetransceiver including a transmitter configured to transmit a terahertzwave, and a receiver configured to receive a reflected terahertz wavereflected by a background reflected object which exists behind an objectto be analyzed; a display; and an information processing apparatusconnected to each of the terahertz wave transceiver and the display,wherein the transmitter irradiates a terahertz wave based on atransmission signal including a specific frequency toward atwo-dimensional area including the object to be analyzed, and theinformation processing apparatus includes: an analysis unit configuredto analyze concentration of the object to be analyzed based on thereflected terahertz wave; and a visualization unit configured togenerate a composite image in which a concentration image of the objectto be analyzed is combined with a background image of the backgroundreflected object based on an analysis result of the analysis unit, anddisplay the composite image on the display.

Advantageous Effects of Invention

According to the present invention, it is possible to provide displaytechnique capable of making it easy to see an analysis result using aterahertz wave. The objects, configurations, and effects other thanthose described above will be clarified by explanation of theembodiments below.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a front view of THz wave detection equipment according to afirst embodiment.

FIG. 1B is a side cross-sectional view of THz wave detection equipmentaccording to the first embodiment.

FIG. 2 is a hardware configuration diagram of THz wave detectionequipment according to the first embodiment.

FIG. 3 is a functional block diagram of THz wave detection equipmentaccording to the first embodiment.

FIG. 4A explains a transmission signal and a reception signal of a THzwave.

FIG. 4B illustrates a signal level of a reception signal.

FIG. 5 illustrates a flowchart of an operation flow of THz wavedetection equipment.

FIG. 6 explains a gas visualization method.

FIG. 7A illustrates an example of image composite processing.

FIG. 7B illustrates an example of image composite processing.

FIG. 8 illustrates appearance of THz wave detection equipment accordingto a second embodiment.

FIG. 9 is a functional block diagram of a controller.

FIG. 10 illustrates an application example of THz wave detectionequipment according to the second embodiment.

FIG. 11A illustrates distance relationship between THz wave detectionequipment and gas to be analyzed.

FIG. 11B illustrates distance relationship between THz wave detectionequipment and gas to be analyzed.

FIG. 12 illustrates a flowchart of a processing flow of THz wavedetection equipment according to a third embodiment, particularlyprocessing by a gas visualization application software unit.

FIG. 13A explains characteristic amounts representing temporal change ina concentration distribution of gas to be analyzed.

FIG. 13B illustrates an example of a concentration distribution diagram.

FIG. 14 illustrates a composite image.

FIG. 15 illustrates a flowchart of a processing flow of a gasvisualization application software unit according to a fourthembodiment.

FIG. 16A is a front view of THz wave detection equipment according to afifth embodiment.

FIG. 16B is a side cross-sectional view of THz wave detection equipmentaccording to the fifth embodiment.

FIG. 17 illustrates a flowchart of a processing flow of a gasvisualization application software unit according to the fifthembodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to the drawings. The components and processing steps which arecommon in the embodiments are provided with the same reference signs,and repetitive explanation thereof will be omitted.

First Embodiment

In a first embodiment, an example in which THz wave detection equipment100 is applied to a gas visualization system will be described. FIG. 1Ais a front view of THz wave detection equipment according to the firstembodiment. FIG. 1B is a side cross-sectional view of the THz wavedetection equipment according to the first embodiment. FIG. 2 is ahardware configuration diagram of the THz wave detection equipmentaccording to the first embodiment.

The THz wave detection equipment 100 illustrated in FIG. 1A isconfigured by externally attaching a THz wave transceiver 1 to asmartphone 10 as an information processing apparatus. The informationprocessing apparatus may be other mobile information terminals, forexample, a tablet terminal. The THz wave detection equipment 100 may beconfigured by connecting the THz wave transceiver 1 to a computer.

As illustrated in FIG. 1B, the smartphone 10 includes an extension I/F125. The THz wave transceiver 1 is connected to the extension I/F 125.

The smartphone 10 includes a display 141 and a front side camera 143 ona front surface thereof. The smartphone 10 further includes a rear sidecamera 144 on a rear surface thereof. The smartphone 10 accommodates aprocessor 107 inside a housing thereof.

FIG. 2 is a block diagram illustrating an example of an internalconfiguration of the smartphone 10. In FIG. 2, the smartphone 10includes a CPU (Central Processing Unit) 101, a system bus 102, a ROM(Read Only Memory) 103, a RAM (Random Access Memory) 104, a storage 110,a communication processing unit 120, the extension interface 125, anoperation unit 130, a video processor 140, an audio processor 150, and asensor 160.

The CPU 101 is a microprocessor unit configured to control the entire ofthe smartphone 10. The system bus 102 is a data communication channelfor transmitting and receiving data between the CPU 101 and eachoperation block in the smartphone 10.

The ROM 103 is a memory in which a basic operation program such as anoperating system and other operation programs are stored. As the ROM103, for example, a rewritable ROM such as an EEPROM (ElectricallyErasable and Programmable Read Only Memory) or a flash ROM is used. TheRAM 104 is a work area at the time of execution of the basic operationprogram and other operation programs. The ROM 103 and the RAM 104 may beconfigured to be integrated with the CPU 101. Furthermore, the ROM 103may use a part of a storage area in the storage 110 instead ofconfiguring it independently as illustrated in FIG. 2. The processor 107is configured by connecting the CPU 101, the ROM 103, the RAM 104 andthe storage 110 via the system bus 102.

The storage 110 stores such as operation programs and operation settingvalues of the smartphone 10, images captured by the smartphone 10, andinformation of the user of the smartphone 10.

Some or all of the functions of the ROM 103 may be substituted with apartial area of the storage 110. The storage 110 needs to hold storedinformation even when the smartphone 10 is not supplied with power fromthe outside. Thus, for example, a device such as a flash ROM, an SSD(Solid State Drive), or an HDD (Hard Disk Drive) is used.

Each of the operation programs stored in the ROM 103 or the storage 110can be updated and the functions thereof can be extended by performingdownload processing from each server device (not illustrated) on thewide area public network.

The communication processing unit 120 includes a LAN (Local AreaNetwork) communication unit 121, a telephone network communication unit122, an NFC (Near Field Communication) communication unit 123, and aBluetooth (registered trademark) communication unit 124. The LANcommunication unit 121 is connected to the wide area public networkthrough an access point (AP) device (not illustrated) by wirelessconnection using Wi-Fi (registered trademark) etc., to transmit andreceive data to and from each server device on the wide area publicnetwork. The telephone network communication unit 122 performs telephonecommunication (telephone call) and transmits and receives data bywireless communication with a base station (not illustrated) of themobile telephone communication network. The NFC communication unit 123performs wireless communication when coming close to the correspondingreader and writer. The Bluetooth communication unit 124 transmits andreceives data with the corresponding terminal by wireless communication.Here, it is assumed that each of the LAN communication unit 121, thetelephone network communication unit 122, the NFC communication unit123, and the Bluetooth communication unit 124 includes an encodingcircuit, a decoding circuit, an antenna, etc. The communicationprocessing unit 120 may further include other communication units suchas an infrared communication unit.

The extension interface 125 is a group of interfaces for extending thefunctions of the smartphone 10. In the present embodiment, it is assumedthat the extension interface 125 is configured by a video interface, anaudio interface, a USB (Universal Serial Bus) interface, a m s memoryinterface, etc. The video interface performs input of video signals froman external video output device, and output of video signals to theexternal video input device. The audio interface performs input of audiosignals from an external audio output device, and output of audiosignals to the external audio input device. The USB interface isconnected to such as a PC (Personal Computer) to transmit and receivedata. The USB interface may be used for connection of a keyboard orother USB devices. The memory interface is used for connection of amemory card and/or other memory media to transmit and receive data.

The operation unit 130 is an instruction input device for inputting anoperation instruction to the smartphone 10. In the present embodiment,it is assumed that the operation unit 130 is configured by an operationkey in which a touch screen and a button switch placed upon the display141 are arranged. In this connection, the operation key may include onlyone of the touch screen and the button switch, and moreover, thesmartphone 10 may be operated by using a keyboard or the like connectedto the extension interface 125. Alternatively, the smartphone 10 may beoperated by using another mobile terminal device connected thereto bywired communication or wireless communication. Still further, thefunction included in the display 141 may be used instead of the functionof the touch screen.

The video processor 140 includes the display 141, an image signalprocessor 142, the front side camera 143, and the rear side camera 144.The front side camera 143 is a camera disposed on a surface (frontsurface) on which the display 141 is also disposed. The front sidecamera 143 is used for, for example, a so-called self-photographingwhich allows the user to capture an image of his or her face by thefront side camera 143 while checking it on the display 141. The rearside camera 144 is a camera disposed on the opposite side (back surface)of the display 141.

The display 141 is a display device such as a liquid crystal panel. Thedisplay 141 displays image data which has been processed by the imagesignal processor 142 to provide the user of the smartphone 10 with theimage data. The image signal processor 142 includes a video RAM (notillustrated), and the display 141 is driven based on the image datainput to the video RAM. The image signal processor 142 has functions ofconverting formats, superimposing menus and other OSD (On-ScreenDisplay) signals, and so on. The front side camera 143 and the rear sidecamera 144 correspond to a camera unit which functions as an imagecapture device configured to convert light input from a lens by using anelectronic device such as a CCD (Charge-Coupled Device) or a CMOS(Complementary Metal Oxide Semiconductor) sensor into an electric signalso as to input image data of the surrounding and an object.

The audio processor 150 includes a speaker 151, an audio signalprocessor 152, and a microphone 153. The speaker 151 provides the userof the smartphone 10 with an audio signal which has been processed bythe audio signal processor 152. The microphone 153 converts such as thevoice of the user into voice data to input the voice data.

The sensor 160 is a group of sensors for detecting a state of thesmartphone 10. In the present embodiment, the sensor 160 includes a GPS(Global Positioning System) receiver 161, a gyro sensor 162, ageomagnetic sensor 163, an acceleration sensor 164, an illuminancesensor 165, and a human sensor 166. With the group of sensors above, itis possible to detect such as the position, inclination, direction,movement, and peripheral brightness of the smartphone 10. The smartphone10 may further include other pressure sensors such as a barometricpressure sensor. The position information is acquired by the GPSreceiver 161. Meanwhile, when the position information cannot beacquired such as in a place where GPS radio waves are difficult to bereceived, it may be acquired based on the position information of the APdevice of Wi-Fi through the LAN communication unit 121, or may beacquired based on the base station information through the telephonenetwork communication unit 122.

The configuration example of the smartphone 10 illustrated in FIG. 2includes components which are not necessarily required in the presentembodiment, such as the communication processing unit 120. Even if thesecomponents are not included, the advantageous effects of the presentembodiment will not be impaired. In addition, other components which arenot illustrated herein, such as a digital broadcast reception functionand an electronic money settlement function, may be further included.

FIG. 3 is a functional block diagram of the THz wave detection equipment100 according to the first embodiment. In the THz wave detectionequipment 100, the THz wave transceiver 1 and the rear side camera 144are connected to an input stage of the processor 107, and the display141 is connected to an output stage of the processor 107.

The processor 107 mainly includes an analysis unit 2 and a visualizationunit 4. The analysis unit 2 and the visualization unit 4 are configuredby executing software that realizes the functions of the THz wavedetection equipment 100 by means of hardware included the processor 107.

The THz wave transceiver 1 includes a transmitter 11, a receiver 12, atransmission controller 13, and an antenna 14.

The THz wave transceiver 1 irradiates a transmission wave 15 a toward athree-dimensional space including gas 6 to be analyzed from the antenna14 attached to the THz wave transceiver 1. The gas 6 to be analyzedabsorbs a specific frequency spectrum. Then, the antenna 14 receives areflected terahertz wave 15 b which has been reflected by a backgroundreflected object 5 and passed through the gas 6 to be analyzed.

The transmission controller 13 controls the transmitter 11 to output aTHz wave (transmission signal) in which the frequency of the spectrum isswept. The transmitter 11 converts the transmission signal into thetransmission wave 15 a (THz wave), and irradiates the transmission wave15 a toward a two-dimensional area including the gas 6 to be analyzedfrom the antenna 14. The receiver 12 acquires the reflected terahertzwave 15 b which has been received by the antenna 14, and converts it toa reception signal and transmits the reception signal to the analysisunit 2.

The irradiation of the transmission wave 15 a to the two-dimensionalarea is performed by scanning an irradiation direction horizontally orvertically in a unit of a period for sweeping the frequency of thespectrum. As a means of scanning the irradiation direction, a mechanicalmeans using such as a galvano mirror may be employed, or an electricalmeans using a phased array antenna in which a plurality of antennaelements is arranged in an array so as to make phases of THz wavesignals to be inputted to each antenna element different may beemployed. A synchronous signal of scanning is shared with thevisualization unit 4.

The analysis unit 2 includes a frequency deference detector 21, a wavedetector 22, a frequency detector 23, a reflection distance calculationunit 24, a reference level detection unit 25, an attenuation leveldetection unit 26, a normalized concentration calculation unit 27, anattenuation ratio calculation unit 28, and a gas identification unit 29.

The visualization unit 4 includes a depth image generation unit 41, aconcentration image generation unit 42, a graphic image generation unit43, and an image composition unit 44.

The frequency deference detector 21 is configured to acquire a frequencydifference Δf0 between the transmission signal and the reception signalbased on an interference signal therebetween, and output the acquiredfrequency difference Δf0 to the reflection distance calculation unit 24.

The reflection distance calculation unit 24 is configured to calculate areflection distance d between the antenna 14 and the backgroundreflected object 5 based on the frequency difference Δf0, and output thecalculated reflection distance d to each of the normalized concentrationcalculation unit 27 and the depth image generation unit 41.

The wave detector 22 is configured to detect an envelope of thereception signal, and output the detected envelope to each of thereference level detection unit 25 and the attenuation level detectionunit 26.

The reference level detection unit 25 is configured to detect, based onthe envelope of the reception signal, a reference level R in a frequencyrange in which the gas 6 to be analyzed does not absorb the spectrum ofthe THz wave. The reference level detection unit 25 outputs the detectedreference level R to the attenuation ratio calculation unit 28.

The attenuation level detection unit 26 is configured to detect, basedon the envelope of the reception signal, a recess of the envelope at aspecific frequency in which the gas 6 to be analyzed absorbs thespectrum so as to detect an attenuation level S based on an amount ofthe recess. The attenuation level detection unit 26 outputs the detectedattenuation level S to the attenuation ratio calculation unit 28.

The attenuation level detection unit 26 is configured to output a timingat which the recess is generated to the frequency detector 23. Thefrequency detector 23 is configured to detect a frequency f1 of thereception signal in which the recess is generated, and output thedetected frequency f1 to the gas identification unit 29.

The gas identification unit 29 is configured to identify a type of gasof which frequency of the absorption spectrum is f1, and output theidentified type to the graphic image generation unit 43.

The attenuation ratio calculation unit 28 is configured to calculate anattenuation ratio R/S based on the reference level R and the attenuationlevel S, and output the calculated attenuation ratio R/S to thenormalized concentration calculation unit 27.

The normalized concentration calculation unit 27 is configured tocalculate a normalized concentration R/S/d obtained by dividing theattenuation ratio R/S by the reflection distance d. The normalizedconcentration calculation unit 27 outputs the normalized concentrationR/S/d to the concentration image generation unit 42.

The rear side camera 144 includes an image capture unit 1441 and acamera controller 1442. The image capture unit 1441 includes an imagecapture device such as a CMOS sensor, and an image capture lens. Theimage capture unit 1441 is configured to capture a visible light imageor an infrared light image in the two-dimensional area in which the THzwave is irradiated. The camera controller 1442 is configured to converta signal from the image capture unit 1441 into an RGB signal. In thisconnection, a part of an image capture area may be configured tocorrespond to an irradiation area of the THz wave signal. In the samemanner as the rear side camera 144, the front side camera 143 includesan image capture unit 1431 and a camera controller 1432. An embodimentusing the front side camera 143 will be described later as a thirdembodiment.

Upon receipt of the reflection distance d, the depth image generationunit 41 is configure to convert the reflection distance d into a singlecolor with variable intensity in accordance with an irradiation scanningsynchronization of the THz wave, so as to generate a two-dimensionalimage.

Upon receipt of the normalized concentration R/S/d, the concentrationimage generation unit 42 is configured to convert the normalizedconcentration R/S/d into a single color with variable intensity or mapit to a predetermined color in accordance with an irradiation scanningsynchronization of the THz wave, so as to generate a two-dimensionalimage.

The graphic image generation unit 43 is configured to acquire text dataas information of the type of gas, and further convert the text datainto graphic image data so as to obtain a graphic image.

Upon receipt of the depth image, the concentration image, the graphicimage, and further a camera image, the image composition unit 44 isconfigured to combine them so as to output a composite image to thedisplay 141.

FIG. 4 explains an analysis method of gas and smell, which mainlyrelates to the THz wave transceiver 1 of FIG. 1 and the analysis unit 2.

FIG. 4A explains a transmission signal 201 and a reception signal 202 ofa THz wave. The transmission wave 15 a and the reflected terahertz wave15 b are in the relationship between being inside and outside of theantenna 14, respectively. FIG. 4A illustrates the transmission signal201 and the reception signal 202 with respect to three axes, i.e., time,signal level, and frequency.

The transmission signal 201 illustrated by a broken line performs asweep operation for gradually changing the frequency in a THz waveregion in a unit time Tm while keeping the signal level constant. Afrequency range in the sweep operation is indicated by B. Aftercompleting the sweep operation in one unit, the transmission signal 201performs a next sweep operation while making an irradiation locationdifferent from that of the previous operation in accordance withscanning of the irradiation described above.

The reception signal 202 illustrated by a solid line is slightly delayedrelative to the transmission signal 201 since the reception signal 202reciprocates the reflection distance d. Due to this delay, when they areobserved at the same time, the frequency difference Δf0 exists betweenthe transmission signal 201 and the reception signal 202. The signallevel of the reception signal 202 is recessed at the specific frequencyf1. This is because the gas 6 to be analyzed absorbs spectrum at thefrequency f1.

FIG. 4B illustrates the signal level of the reception signal 202. Asexplained in FIG. 4B, the signal level is recessed at the frequency f1.The reference level R is a signal level at the time without absorptionby gas, and can be obtained by sampling a plurality of points in flatportions excluding a recessed portion and by averaging them. The signallevel S of the recessed portion is a signal level attenuated by gasabsorption, and represents a level of gas absorption. The higher the gasconcentration is, the greater the attenuation is and the smaller theattenuation level S becomes. The attenuation ratio due to gas absorptionis indicated by R/S.

The reflection distance calculation unit 24 calculates the reflectiondistance d by Equation (1) below.

$\begin{matrix}\left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack & \; \\{d = {\frac{{cT}_{m}}{2B}\Delta\; f_{0}}} & (1)\end{matrix}$

d: Reflection distanceC: speed of light

The normalized concentration calculation unit 27 calculates a normalizedgas concentration (also referred to as a normalized concentration) byEquation (2) below.

[Equation 2]

Normalized gas concentration=R/S/d  (2)

FIG. 5 illustrates a flowchart of an operation flow of the THz wavedetection equipment 100.

After being activated, the THz wave detection equipment 100 performsinitial settings (step S10). The THz wave detection equipment 100performs image capture processing by the rear side camera 144 (step S11)and measurement by the THz wave transceiver 1 in parallel. Themeasurement by the THz wave transceiver 1 includes a series ofprocessing steps, i.e., irradiation control of a THz wave with respectto an object to be analyzed (in the present embodiment, the entire areaincluding the gas to be analyzed) (step S12), irradiation of the THzwave (step S13), and reception of reflected terahertz wave (step S14).The steps from S12 to S14 are included in a THz wave control process S1,and in step S12, control for irradiating the THz wave toward an area tobe irradiated is performed. For example, an irradiation level of the THzwave, a time unit for a sweep operation, and a frequency width arecontrolled therein. In step S13, execution of irradiation of the THzwave is instructed so as to obtain a detection signal of a receptionsignal, which is the reflected terahertz wave, in step S14.

After receiving the reflected terahertz wave (step S14), frequencydifference detection processing (step S15) by the frequency deferencedetector 21, reference level detection processing (step S16) by thereference level detection unit 25, attenuation level detectionprocessing (step S17) by the attenuation level detection unit 26, andfrequency detection processing (step S18) by the frequency detector 23are performed in parallel. The steps from S15 to S25 are included in ananalysis process S2.

After the frequency difference detection process (step S15) iscompleted, the reflection distance calculation unit 24 calculates thereflection distance d (step S19) and records the calculated reflectiondistance d in the RAM 104 or the storage 110 (step S23). Then, thereflection distance calculation unit 24 outputs the reflection distanced to the depth image generation unit 41, and the depth image generationunit 41 generates a depth image 51 (see FIG. 6) (step S26).

After the reference level detection processing (step S16) is completed,the attenuation ratio calculation unit 28 calculates the gas attenuationrate R/S (step S20). Next, the normalized concentration calculation unit27 performs normalized concentration calculation processing (step S21),and records the normalized gas concentration in the RAM 104 or thestorage 110 (step S24). Then, the normalized concentration calculationunit 27 outputs the normalized concentration R/S/d to the concentrationimage generation unit 42, and the concentration image generation unit 42generates a concentration image 52 (see FIG. 6) (step S27)

After the attenuation level detection processing (step S17) iscompleted, the frequency detector 23 detects the recessed (attenuated)frequency f1 (step S18). Based on the detected frequency f1, the gasidentification unit 29 specifies the type of gas, i.e., identifiescomponents of the gas (step S22), and records the identified componentsof the gas in the RAM 104 or the storage 110 (step S25). Then, the gasidentification unit 29 outputs an identification result of thecomponents as text data to the graphic image generation unit 43, and thegraphic image generation unit 43 generates a graphic image 53 (see FIG.6) (step S28).

The rear side camera 144 captures a background image (step S11) toacquire a camera image (step S29).

The image composition unit 44 acquires the depth image 51, theconcentration image 52, the graphic image 53, and a camera image 54,combines these four images (step S30), and displays a composite image onthe display 141 (step S31).

The CPU 101 determines whether a condition for determining whetherrepetition is necessary is satisfied (step S32). The condition above is,for example, whether scanning has been completed or whether theapplication software should be continued. When the CPU 101 determinesthat the repetition is necessary (step S32/Yes), the processing returnsto step S11 and step S12. When the CPU 101 determines that therepetition is not necessary (step S32/No), the processing is terminated.

FIG. 6 explains a gas visualization method.

The depth image 51 is a two-dimensional image obtained, for example, byconverting the reflection distance d into a single color with variableintensity in accordance with the irradiation scanning synchronization ofthe THz wave. Since the THz wave has a long wavelength relative tovisible light, definition of the depth image 51 is inferior to that ofthe camera image captured by the visible light. The depth image 51 isobtained by visualizing the reflection distance d to the backgroundreflected object, in which a background covered with aerosol, etc. canbe observed. Accordingly, the depth image 51 together with the cameraimage 54 makes it easy to recognize such as an obstacle and an emergencyexit for evacuation. A range corresponding to the relationship between arange for two-dimensionally scanning the THz wave and an angle of viewof the camera image is detected and stored in advance.

The concentration image 52 of the gas is a two-dimensional imageobtained, for example, by converting the normalized concentration R/S/dinto a single color with variable intensity or by performing colormapping in accordance with the irradiation scanning synchronization ofthe THz wave in the same manner as the depth image 51. Since the gasconcentration R/S is normalized by using the reflection distance d, itis possible to visualize danger of the gas in terms of concentration anddistance.

The graphic image 53 is obtained by converting text data of the type ofthe gas into graphic image data. The graphic image 53 is useful since itmay serve as an auxiliary image for visualizing such as, in addition tothe type of gas, a warning message in accordance with the level ofdanger, temporal change of the gas, or both of them, in aneasy-to-understand manner.

The camera image 54 is a camera image captured by the rear side camera144. Since the camera image 54 is obtained by imaging the visible lightreflected by the background reflected object 5, it is referred to as abackground image.

A composite display image 55 is an image obtained by combining the depthimage 51, the concentration image 52, the graphic image 53, and thecamera image 54, which corresponds to an image to be displayed. The fourimages are four-layer images of a composite image, and by performingalpha blending as a composite method, a composite image that is easy tobe visually recognized can be obtained. In this connection, the depthimage 51 and the camera image 54 may be complementarily used. When thecamera image 54 is unstable in an environment such as including aerosol,combining images may be performed to mainly display the depth image 51or replace a part of the camera image 54 with the depth image 51.Furthermore, based on the camera image 54 and the depth image 51,combining images may be performed to display a feature portion such asan exit door, an obstacle on an evacuation route, or both of them whichhave been recognized from the camera image 54.

The image composition unit 44 acquires the depth image 51, theconcentration image 52, the graphic image 53, and the camera image 54.Then, the image composition unit 44 compares the camera image 54 and thedepth image 51 to acquire an object distance in the camera image 54.Next, the image composition unit 44 compares the concentration image 52and the depth image 51 to determine whether gas 520 displayed in theconcentration image 52 is in front of or behind the object in the cameraimage 54. In the composite display image 55 illustrated in FIG. 6,comparison of a distance from the THz wave detection equipment 100 tothe seat in the depth image 51 with a distance from the THz wavedetection equipment 100 to the gas 520 shows that the distance from theTHz wave detection equipment 100 to the gas 520 is shorter than theother distance. Accordingly, the gas 520 is superimposed on the seatcaptured in the depth image 51 so as to be displayed in front of theseat.

FIG. 7A and FIG. 7B illustrate examples of image composite processing. Aconcentration image 521 and a camera image 541 illustrated in FIG. 7Aare the same as those illustrated in FIG. 7B. On the other hand, a depthimage 511 illustrated in FIG. 7A and a depth image 512 illustrated inFIG. 7B are different to each other. In the depth image 511, a table islocated at a position farther from the THz wave detection equipment 100than the gas while in the depth image 512, the table is located at aposition closer from the THz wave detection equipment 100 than the gas.In the case of FIG. 7A, the image composition unit 44 generates acomposite display image 551 in which the gas is displayed in front ofthe table. In the case of FIG. 7B, the image composition unit 44generates a composite display image 552 in which the gas is displayedbehind the table.

As described above, according to the first embodiment, since theconcentration image 52 of the gas is superimposed on the backgroundimage which is obtained by the depth image 51 or the camera image 54, itis possible to visualize a position of the gas with respect to thebackground image. By using the camera image 54, a background image withhigh resolution can be obtained while in an environment such asincluding aerosol, the background can be confirmed by using the depthimage 51, thereby making it possible to obtain the background image invarious environments. Furthermore, the present embodiment can beutilized not only for analysis of gas but also for analysis performed ata place such as a kitchen where a bad smell may be generated.

Second Embodiment

With reference to FIG. 8 to FIG. 10, the second embodiment will bedescribed. The second embodiment shows an example of THz wave detectionequipment 100 a which is configured by attaching the THz wavetransceiver 1 to a wearable terminal 300. The wearable terminal 300 maybe integrated with the THz wave transceiver 1. A user can use the THzwave detection equipment 100 a in a state in which it is attached to thebody so that he or she can freely move both hands.

FIG. 8 illustrates appearance of the THz wave detection equipment 100 aaccording to the second embodiment. As illustrated in FIG. 8, the THzwave detection equipment 100 a is configured by attaching a THz wavetransceiver 1 a and a camera 3 to the wearable terminal 300.

The wearable terminal 300 includes a top head holder 303, a side headholder 304, an eyeglass optical unit 302 provided in front of the sidehead holder 304, a screen 305 provided further in front of the eyeglassoptical unit 302, and an image projector 301 provided on the top headholder 303.

The THz wave transceiver 1 a and the camera 3 are mounted, for example,on the top of the top head holder 303.

The THz wave detection equipment 100 a further includes a controller 7 bwhich is electrically or communicatively connected to the THz wavetransceiver 1 a, the cameras 3, the image projector 301, the eyeglassoptical unit 302, and the screen 305.

The controller 7 has the functions of the smartphone 10, excluding thefunctions of the camera 3 and the display therefrom. The screen 305, theimage projector 301, and the eyeglass optical unit 302 correspond to thedisplay 141. The top head holder 303 and the side head holder 304 areused to mount the cameras 3, the THz wave transceiver 1 a, and thedisplay on the head of the user of the THz wave detection equipment 100a.

The image projector 301 projects the composite display image 55 onto thescreen 305. At this time, the depth image 51 may be three-dimensionallydisplayed so as to give perspective in accordance with the reflectiondistance d. In this case, the composite display image 55 is composed ofa visual image of the left eye and a visual image of the right eye. Theeyeglass optical unit 302 incorporates an electronic shutter 102 a (seeFIG. 9) therein. When projecting the visual image of the left eye, theeyeglass optical unit 302 controls a left eye side to be in atransmissive state and a right eye side to be in a shielded state by theelectronic shutter. When projecting the visual image of the right eye,the eyeglass optical unit 302 controls the right eye side to be in thetransmission state and the left eye side to be in the shielded state bythe electronic shutter.

The screen 305 may be a semi-transmissive screen. In this case, thecamera image 54 is not included in the composite display image 55. Abackground image which can be seen through the semi-transmissive screen305 is made to be visually recognized together with the compositedisplay image 55 to be projected onto the semi-transmissive screen 305by the image projector 301, which is composed of at least one of thedepth image 51, the concentration image 52, and the graphic image 53.The camera image 54 is used for such as alignment when obtaining thecomposite display image 55. With this configuration, the user can safelyuse the THz wave detection equipment 100 a while viewing an actual imageof the background through the semi-transmissive screen 305.

FIG. 9 is a functional block diagram of the controller 7. The controller7 includes a CPU 71, a RAM 72, a FROM 73, an SD I/F 74 a, an SD memory74 b, a communication I/F 75, a graphic processor 76, a touchscreendisplay 45 a, a USB® I/F 77, and an optical system controller 78. TheUSB® I/F 77 is connected to the THz wave transceiver 1 a and the camera3. The optical system controller 78 is connected to the electronicshutter 102 a to control opening and closing of the electronic shutter102 a.

The THz wave transceiver 1 a includes a USB I/F 14.

The controller expands a program stored in the FROM 73 on the RAM 72 toexecute it on the CPU 71. The FROM 73 includes, as programs relating toanalysis and visualization of gas and smell, a THz wave control processunit 731, a camera control process unit 732, an analysis process unit733, a visualization process unit 734, and a gas visualizationapplication software unit 735. Here, the THz wave control process unit731 relates to an operation of the THz wave transceiver 1, inparticular, the transmission controller 13 illustrated in FIG. 3. Thecamera control process unit 732 relates to an operation of the cameracontroller 1432 for the front side camera 143 or the camera controller1442 for the rear side camera 144 illustrated in FIG. 3. The analysisprocess unit 733 relates to an operation of the analysis unit 2illustrated in FIG. 3. The visualization process unit 734 and the gasvisualization application software unit 735 correspond to thevisualization unit 4 illustrated in FIG. 3.

After being activated, the gas visualization application software unit735 is configured to manage a user interface, as well as call the THzwave control process unit 731, the camera control process unit 732, theanalysis process unit 733, and the visualization process unit 734 toperform analysis and visualization of gas and smell.

The SD memory 74 b is configured to store such as application data, andtransmit and receive the data to and from the CPU 71 through the SD I/F74 a. The communication I/F 75 is a communication interface such as 3Gor 4G mobile communication or a wireless LAN, and is connected to suchas a server (not illustrated) via the Internet. The controller 7 maymake the server execute a part of the program to be executed to reduceits own processing load.

The graphic processor 76 is configured to generate an image to bedisplayed on a display screen of the touchscreen display 45 a based onapplication data generated by the program. The graphic processor 76 alsoobtains camera image data captured by the camera 3 to display it. Thetouchscreen display 45 a includes a touch screen as a user inputoperation unit, in addition to the display screen.

The USB I/F 77 is a serial bus interface, and connected to each of thecontroller 7, the THz wave transceiver 1 a, and the camera 3.

The THz wave transceiver 1 a corresponds to the THz wave transceiver 1according to the first embodiment to which the USB I/F 14 is furthermounted. The USB I/F 14 transmits and receives data with the USB I/F 77of the controller 7. At this time, for example, it may be configured todigitize a detected envelope and transmit and receive it, instead oftransmitting and receiving a reception signal of the THz wave.

FIG. 10 illustrates an application example of the THz wave detectionequipment 100 a according to the second embodiment. THz wave detectionequipment 100 b illustrated in FIG. 10 is integrally configured, forexample, such that the THz wave transceiver 1 and the camera 3 areincorporated in the THz wave detection equipment 100 a or attached inclose contact with the THz wave detection equipment 100 a. The THz wavedetection equipment 100 b includes an opening 31 a of the camera 3 andan antenna 14 a of the THz wave transceiver 1. The THz wave detectionequipment 100 b also incorporates a controller 7 a therein.

The THz wave detection equipment 100 b is communicatively connected to aserver 92 via a communication base station 90 through the Internet 91 bytransmitting and receiving a communication signal 75 a therebetween.

The server device 92 can execute a part of the program to be executed bythe controller 7 to reduce processing load of the controller 7 a. Forexample, the server device 92 may be configured to be notified of thefrequency f1 of the absorption spectrum, identify the type of gascorresponding to the frequency f1 by using a database in the serverdevice 92, and return a result of identification to the controller 7 a.

Alternatively, the server device 92 may be configured to receive thedepth image 51 and the camera image 54 to recognize a characteristicportion of the background image.

In addition, the server device 92 may be configured to identify thelevel of danger with respect to an alert issued by the controller 7 a,and send a notification to the police and/or the fire department, whilemaking the controller 7 a propose a concrete idea for an evacuationinstruction.

As described above, according to the second embodiment, it is possibleto realize gas and smell visualization equipment by utilizing ageneral-purpose information device.

Third Embodiment

With reference to FIG. 11A, FIG. 11B, and FIG. 12, a third embodimentwill be described. The technical feature of the THz wave detectionequipment according to the third embodiment can be found in a functionof measuring a distance to gas.

FIG. 11A illustrates distance relationship between the THz wavedetection equipment 100 b and the gas 6 to be analyzed.

An extension device 80 illustrated in FIG. 11A includes a handle 83, anextension rod 82 attached to one end of the handle 83 to be extended andretracted in a longitudinal direction thereof, and a support base 81mounted on a distal end side of the extension rod 82 (the side oppositeto the handle 83). The THz wave detection equipment 100 b is fixed tothe support base 81. The user grips the handle 83, adjusts the length ofthe extension rod 82, and measures the gas 6 to be analyzed by the THzwave detection equipment 100 b attached to the support base 81 tovisualize a result thereof. The distance between the THz wave detectionequipment 100 b and the gas 6 to be analyzed can be varied in accordancewith the length of the extension rod 82. The THz wave detectionequipment 100 b acquires data of whether the extension rod 82 is in anextended state or a contracted state, together with the measurementdata.

FIG. 11B illustrates distance relationship between the THz wavedetection equipment 100 b and the gas 6 to be analyzed.

In a position P1 of the THz wave detection equipment 100 b, theextension rod 82 is in the contracted state, and an angle facing the gas6 to be analyzed is θ1. On the other hand, in a position P2 of the THzwave detection equipment 100 b, the extension rod 82 is in the extendedstate, the distance to the gas 6 to be analyzed is shorter by ananalysis distance difference l than the distance in the case of P1, andan angle facing the gas 6 to be analyzed is θ2. At this time, a distanceLg to the gas 6 to be analyzed is given by Equation (3) below.

$\begin{matrix}\left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack & \; \\{{Lg} = {l\frac{\tan\;\theta_{1}}{{\tan\;\theta_{2}} - {\tan\;\theta_{1}}}}} & (3)\end{matrix}$

FIG. 12 illustrates a flowchart of a processing flow of the THz wavedetection equipment 100 b according to the third embodiment,particularly the processing by a gas visualization application softwareunit 735.

After being activated, the gas visualization application software unit735 performs initial settings (step S10), and subsequently executes theTHz wave control process (step S1) and the analysis process (step S2).At this time, the extension rod 82 is in the contracted state, and afirst concentration image of the gas 6 to be analyzed is generated (stepS34).

Then, the user extends the extension rod 82 to change the measurementdistance (step S35), and thereafter, the THz wave control process (stepS1) and the analysis process (step S2) are executed again.

The visualization process unit 734 generates a second concentrationimage of the gas 6 to be analyzed (step S36).

The analysis process unit 733 calculates the Equation (3) to obtain thedistance Lg to the gas (step S37).

The analysis process unit 733 recalculates the normalized concentrationR/S/Lg (step S38)

The analysis process unit 733 records the normalized concentrationR/S/Lg (step S24), and obtains a third concentration image (step S39).The steps S34 to S38 are included in a first extended process S4 whichis an extension process of the analysis process S2.

The visualization process unit 734 generates, in addition to the thirdconcentration image (step S39), the depth image 51 (step S26), thegraphic image 53 (step S28), and the camera image 54 (step S29). Then,the image composite processing (step S30) is performed by using thethird concentration image and at least one of the depth image 51, thegraphic image 53, and the camera image 54 to display the compositedisplay image 55 (step S31). When the repetition condition is satisfied(step S32/Yes), a series of processes is repeated, and when therepetition condition is not satisfied (step S32/No), the processing isterminated.

As described above, according to the third embodiment, at the time ofnormalizing the gas concentration, the distance Lg to the gas to beanalyzed is used instead of the reflection distance d to the backgroundreflected object. As a result, the level of danger, etc. represented bythe normalized gas concentration becomes more accurate.

Fourth Embodiment

With reference to FIG. 13A to FIG. 15A, a fourth embodiment will bedescribed. FIG. 13A explains characteristic amounts representingtemporal change in a concentration distribution of the gas 6 to beanalyzed. FIG. 13A illustrates the distribution of the gas 6 to beanalyzed in the two-dimensional area, and the concentration distributionis evaluated by four directions of X+ and X− axes, Y+ and Y− axes, V+and V− axes, and U+ and U− axes with a point having a peak value of theconcentration as reference.

FIG. 13B illustrates an example of the concentration distribution. Theconcentration distribution illustrated in FIG. 13B is an example of theX+ and X− axes, in which a concentration analysis value takes D1, D2, .. . in the X+ direction and takes D−1, D−2, . . . in the X− direction,with a concentration peak value D0 being set as 0 point.

S** in FIG. 13B (** shows an axial direction such as X+ or X−) is avalue for evaluating a level of spread of the concentration distributionillustrated in FIG. 13A, and is obtained by Equation (4) below.Evaluation of spread is performed for each of X+ and X−.

$\begin{matrix}\left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack & \; \\\left. \begin{matrix}{S_{x +} = {\sum\limits_{i = 0}^{N}{{i\hat{}2} \cdot {D_{i}/D_{0}}}}} \\{S_{x -} = {\sum\limits_{i = 0}^{- M}{{i\hat{}2} \cdot {D_{i}/D_{0}}}}}\end{matrix} \right) & (4)\end{matrix}$

FIG. 13B illustrates a table in which values, at the present time t1, ofa coordinate value of a peak concentration value, a peak concentrationvalue, and spread evaluation values S_(x)−, S_(x)+, S_(y)−, S_(y)+,S_(u)−, S_(u)+, S_(v)−, S_(v)+, and values, at the previous time t0,thereof are recorded, and temporal change evaluation values of spread ofthe gas concentration distribution are calculated in the right column.

FIG. 14 illustrates a composite display image 553 to be displayed in thepresent embodiment. In the composite display image 553, graphic imageswhich allow the spread of the distribution to be easily seen aresuperimposed on the composite display image 55 (see FIG. 6) of the firstembodiment. The composite display image 553 is obtained by superimposingG10, G11, G12, and G13 on the composite display image 55. Here, G10represents change in the concentration peak coordinates (R, φ), and G11and G12 represent values having large change amounts, which have beenselected among the temporal change evaluation values of S_(x)− toS_(v)+. The size of each arrow of G1, G2, and G3 corresponds to eachevaluation value. The temporal change of spread of gas above is used forprediction of a dangerous area, and advice for an evacuation directionis given by displaying G13.

FIG. 15 illustrates a flowchart of a processing flow of the gasvisualization application software unit 735 according to the fourthembodiment. After being activated, the gas visualization applicationsoftware unit 735 performs initial settings (step S10), and subsequentlyexecutes the THz wave control process S1 and the analysis process S2.

The gas visualization application software unit 735 reads out therecorded concentration data (step S40) to detect a position where theconcentration has a peak value (step S41). In the case of analyzing aplurality of types of gas, the gas visualization application softwareunit 735 performs the steps above for each type of gas.

Next, the gas visualization application software unit 735 calculatesvalues of evaluation parameters such as spread of the distribution (stepS42) and records the calculated values (step S43).

The gas visualization application software unit 735 reads out values ofevaluation parameters such as spread of the distribution at the previoustime (step S44) to calculate temporal change of for the parameters (stepS45). The gas visualization application software unit 735 selects anevaluation parameter having significant temporal change (step S46).

The gas visualization application software unit 735 detects an exit, anobstacle on an evacuation route, or both of them based on the backgroundimage (step S47) to determine recommendation of an evacuation direction(step S48). The steps S40 to S49 are included in a second extendedanalysis process S5 which is an extension process of the analysisprocess S2.

The gas visualization application software unit 735 transmits theevaluation parameter having the significant value and the evacuationdirection to the display process S3 (step S49).

The gas visualization application software unit 735 generates thecomposite display image 553 illustrated in FIG. 14, and displays thegenerated composite display image 553 on the display 141 (step S3).Then, when the processing is determined not to be continued in step S32,the processing is terminated.

As described above, according to the fourth embodiment, evaluationvalues corresponding to the temporal change of the gas concentrationdistribution are calculated to predict temporal change of a dangerousarea, and accordingly, it is possible to display an instruction of aneffective evacuation route, etc. in the composite image.

Fifth Embodiment

With reference to FIG. 16 and FIG. 17, a fifth embodiment will bedescribed. FIG. 16A is a front view of THz wave detection equipment 100c according to the fifth embodiment. FIG. 16B is a side cross-sectionalview of the THz wave detection equipment 100 c according to the fifthembodiment.

The THz wave detection equipment 100 c illustrated in FIG. 16A includesa THz wave transceiver 1 a which is accommodated in a housing cover 410to cover the controller 7. The THz wave detection equipment 100 c isconfigured to analyze the smell of the user while capturing an image ofthe user himself or herself by the front side camera 143. The THz wavedetection equipment 100 c is used to detect the ingredients of fragrancecontained in, for example, laundry softener so as to assist for payingattention not to disturb the people around the user.

The THz wave detection equipment 100 c includes a touchscreen display 45a. An image of the user is displayed on the touchscreen display 45 a,and marks G14 are superimposed on the image of the user. Each shape ofthe marks G14 corresponds to causes of the smell registered in advance,respectively, and the level of the smell is indicated by the number ofhorizontal bars G15 at the top of a screen.

FIG. 17 illustrates a flowchart of a processing flow of the gasvisualization application software unit 735 according to the fifthembodiment. After being activated, the gas visualization applicationsoftware unit 735 performs initial settings (step S10), and subsequentlyexecutes the THz wave control process S1 and the analysis process S2.

The gas visualization application software unit 735 recognizes a personarea from a camera image received from step S29 (step S50) to generate aconcentration image of the person area (step S27). The gas visualizationapplication software unit 735 generates graphic images by using theconcentration image (step S28) to create such as the marks G14illustrated in FIG. 16A (step S29).

The gas visualization application software unit 735 performs imagecomposite processing to generate a composite display image 554 (stepS30), and displays the composite display image 554 on the touchscreendisplay 45 a (step S31). Then, when the processing is determined not tobe continued in step S32, the processing is terminated.

As described above, according to the fifth embodiment, it is possible toeasily analyze the smell of the user himself/herself by utilizing acamera unit of a smartphone, which is provided for self-photographing,etc.

The present invention is not limited to each of the embodimentsdescribed with reference to FIG. 1 to FIG. 17, and a part of theconfiguration in one embodiment can be replaced with that in the otherembodiments. It is also possible to add the configuration of oneembodiment to the other embodiments. All the modifications describedabove belong to the scope of the present invention. Furthermore,numerical values, messages, etc. appearing in the text and drawings aremerely examples, and the effects of the present invention are notimpaired even if different ones are used.

A part or all of the functions of the present invention may beimplemented by hardware, for example, by designing them with anintegrated circuit. They may be implemented by software by executing anoperation program by the microprocessor unit, a CPU, etc. In addition,the scope of software implementation is not limited, and hardware andsoftware may be used in combination.

In the embodiments above, an object to be detected is the gas 6 to beanalyzed, and the background reflected object is a scene in the realspace where the gas 6 to be analyzed floats, which is for example, aspace in a vehicle and a structure in a living room. Meanwhile, the THzwave detection equipment 100 may be used as detection equipment atproduct shipment. In this case, a background reflected object is aproduct and the object to be detected is a foreign substance in theproduct, and the THz wave detection equipment 100 may be used to detectthe foreign substance mixed in such as a food. The THz wave detectionequipment 100 may be used as detection equipment for detectingcontamination of a foreign substance into a non-food product, such as atire. The THz wave detection equipment 100 may be used as pharmaceuticalshipping detection equipment for coating inspection of multilayer coatedchemical. The THz wave detection equipment 100 may be used in a baggageinspection station of such as an airport so as to specify a content of aPET bottle or a content in a suitcase without unlocking it.

REFERENCE SIGNS LIST

-   1: THz wave transceiver-   2: analysis unit-   3: camera-   4: visualization unit-   5: background reflected object-   6: gas to be analyzed-   7: controller-   10: smartphone-   11: transmitter-   12: receiver-   13: transmission controller-   14: antenna-   15 a: transmission wave-   15 b: reflected terahertz wave-   45 a: touchscreen display

1. Terahertz wave detection equipment comprising: a terahertz wavetransceiver including a transmitter configured to transmit a terahertzwave and a receiver configured to receive a reflected terahertz wavereflected by a background reflected object which exists behind an objectto be analyzed; a display; and an information processing apparatusconnected to each of the terahertz wave transceiver and the display,wherein the transmitter irradiates a terahertz wave based on atransmission signal including a specific frequency toward atwo-dimensional area including the object to be analyzed, and theinformation processing apparatus includes: an analysis unit configuredto analyze concentration of the object to be analyzed based on thereflected terahertz wave; and a visualization unit configured togenerate a composite image in which a concentration image of the objectto be analyzed is combined with a background image of the backgroundreflected object based on an analysis result of the analysis unit, anddisplay the composite image on the display.
 2. The terahertz wavedetection equipment according to claim 1, wherein the transmitterirradiates a terahertz wave based on a transmission signal in which afrequency is swept, the analysis unit includes: a frequency deferencedetection unit configured to detect a frequency difference between afrequency of the terahertz wave transmitted by the transmitter and afrequency of the reflected terahertz wave received by the receiver; areflection distance calculation unit configured to calculate areflection distance from the terahertz wave transceiver to thebackground reflected object based on the frequency difference; anormalized concentration calculation unit configured to calculate anormalized concentration of the object to be analyzed which has beennormalized by a distance based on a level of the terahertz wavetransmitted from the transmitter, an amount of attenuation of thereflected terahertz wave relative to the terahertz wave irradiated bythe transmitter, and the reflection distance; and an objectidentification unit configured to specify a type of the object to beanalyzed based on a frequency attenuated in the reflected terahertzwave, the visualization unit includes: a concentration image generationunit configured to generate a concentration image including variousdisplay modes which differ in accordance with the normalizedconcentration; a graphic image generation unit configured to generate agraphic image indicating the type of the object to be analyzed; and animage composition unit configured to combine the concentration image andthe graphic image with the background image to generate a compositeimage, and display the composite image on the display.
 3. The terahertzwave detection equipment according to claim 2, wherein the visualizationunit further includes a depth image generation unit configured togenerate a depth image including various display modes which differ inaccordance with the reflection distance, and the image composition unitis further configured to use the depth image as the background image,and combine the concentration image with the depth image to generate thecomposite image.
 4. The terahertz wave detection equipment according toclaim 2, wherein the information processing apparatus is connected to acamera which captures an image of visible light to generate a cameraimage, and the image composition unit is further configured to use thecamera image as the background image, and combine the concentrationimage with the camera image to generate the composite image.
 5. Theterahertz wave detection equipment according to claim 2, wherein thenormalized concentration calculation unit is further configured tocalculate the normalized concentration by an equation (1) below, where asignal level of a flat portion without absorption by the object to beanalyzed is R, a signal level of a frequency attenuated by absorption ofthe terahertz wave by the object to be analyzed is S, and the reflectiondistance is dNormalized concentration=R/S/d  (1).
 6. The terahertz wave detectionequipment according to claim 1, wherein the object to be analyzed isinvisible gas, the concentration image is an image illustrating aconcentration distribution of the gas, and the composite image is animage obtained by superimposing the image illustrating the concentrationdistribution of the gas on the background image.
 7. The terahertz wavedetection equipment according to claim 2, wherein the THz wave detectionequipment is attached to an extension device that includes a supportbase for supporting the THz wave detection equipment and an extensionrod connected to the support base, the THz wave detection equipmentmeasures the object to be analyzed a plurality of times by varying anextension amount of the extension rod, the normalized concentrationcalculation unit is further configured to: calculate a maximum angle θ₁and a maximum angle θ₂ obtained by each measurement of a width directionbetween ends of the object to be analyzed which is performed by the THzwave detection equipment; calculate a distance Lg from the THz wavedetection equipment to the object to be analyzed by an equation (2)below, where an analysis distance difference which is a differencebetween each of the amount of extension in each measurement is l; andcalculate the normalized concentration by an equation (3) below where asignal level of a flat portion without absorption by the object to beanalyzed is R, a signal level of a frequency attenuated by absorption ofthe terahertz wave by the object to be analyzed is S, and the distancefrom the THz wave detection equipment to the object to be analyzed isLg,Lg=l tan θ₁/(tan θ₂−tan θ₁)  (2)Normalized concentration=R/S/Lg  (3), and the concentration imagegeneration unit is further configured to generate a new concentrationimage in which the normalized concentration is updated.
 8. The terahertzwave detection equipment according to claim 1, wherein the visualizationunit includes a graphic image generation unit configured to acquire aconcentration distribution over a plurality of axes for each of aplurality of concentration images generated along a time-series, andobtain values of evaluation parameters corresponding to a center of theconcentration distribution and spread of the concentration distribution,to generate graphic image data indicating a time-series change of thevalues of the evaluation parameters, and an image composition unitconfigured to combine the graphic image data with the background imageto generate a composite image, and display the composite image on thedisplay.
 9. The terahertz wave detection equipment according to claim 8,wherein the graphic image generation unit is further configured togenerate a graphic image indicating a path in a direction different froma direction of change of a position in the concentration distributionalong the time series based on the time series change of the values ofthe evaluation parameters, and combine the graphic image with thebackground image to generate the composite image.
 10. The terahertz wavedetection equipment according to claim 4, wherein the object to beanalyzed is a component of smell, the object identification unit isfurther configured to identify the component of the smell based on thereflected terahertz wave, the graphic image generation unit is furtherconfigured to generate a graphic image indicating a type of thecomponent of the smell as specified, and the image composition unit isfurther configured to specify a region of the camera image, whichincludes an image of a real space where the component of the smell isdetected is captured, and generate a composite image in which thegraphic image indicating the type of the component of the smell asspecified is superimposed on the region.
 11. A terahertz wave detectionmethod comprising the steps of: irradiating a terahertz wave based on atransmission signal including a specific frequency toward atwo-dimensional area including an object to be analyzed; receiving areflected terahertz wave reflected by a background reflected objectwhich exists behind the object to be analyzed; analyzing concentrationof the object to be analyzed based on the reflected terahertz wave;generating a composite image in which a concentration image of theobject to be analyzed is combined with an image of the backgroundreflected object based on a result of analysis of the concentration ofthe object to be analyzed; and displaying the composite image on adisplay.
 12. A terahertz wave detection system comprising: a terahertzwave transceiver including a transmitter configured to transmit aterahertz wave and a receiver configured to receive a reflectedterahertz wave reflected by a background reflected object which existsbehind an object to be analyzed; a wearable terminal including adisplay; and an information processing apparatus connected to each ofthe terahertz wave transceiver and the wearable terminal, wherein theterahertz wave transceiver irradiates a terahertz wave based on atransmission signal including a specific frequency toward atwo-dimensional area including the object to be analyzed, and theinformation processing apparatus includes: an analysis unit configuredto analyze concentration of the object to be analyzed based on thereflected terahertz wave; and a visualization unit configured togenerate a composite image in which a concentration image of the objectto be analyzed is combined with an image of the background reflectedobject based on an analysis result of the analysis unit, and output thecomposite image to the wearable terminal.